I was wondering if anyone has tried making a sleeping bag liner / sheet out of the 1.1oz ripstop nylon? I am looking to get some uncoated lightweight material to make a decent liner/sheet to extend the life of my sleeping bags/quilts and sleeping pads.

One thing I've heard about nylon is that it gets softer if you wash it a couple times. I am torn between trying to make this out of polyester or nylon. Silk is too expensive, I'm looking to make this for about $10 - $15 each. and keep the weight under 6oz.

Actually, silk isn't a bad choice. If you buy thin stuff from the right place, it is about the same price as nylon, and it is probably lighter in weight. I sewed a silk liner that came in around 2.5 ounces. Silk can represent a challenge to the sewist.

The trick is to use safety pins to pin the strong parts of the liner (like, the sewn seam) to the strong parts of the inside of the sleeping bag. That way, the liner stays with the sleeping bag, and it doesn't get twisted around your feet.